mara (#4172): the components page was out of date against its own
stated rule ("a new primitive gets a section here the same day it's
added"). Dialog and ConfirmDialog are real standalone exported
primitives (AgentsPage uses both directly) with no demo section.
FormField deliberately stays excluded — its own comment already says
it's not a reachable primitive, just TextField/SelectField's shared
internal wrapper, so it was never meant to get one.
Also gave the Table demo's "detail" column a multiselect filter, so
the checkbox popover and reset-filters button — real, daily-used Table
behavior — are actually shown rather than an unfiltered grid.